Four countries - Brazil, Germany, India and Japan - have grouped together to press their claim for permanent membership of the United Nations Security Council.

BBC News Online examines the issues involved.

Why change the Security Council?

The Security Council was formed after World War II and the winners - the US, the Soviet Union, China, Britain and France - gave themselves permanent seats with a veto. The Council's membership has been enlarged from 11 to 15 but the permanent members have not changed and nor has the power of veto.

Many countries feel that the structure is unbalanced. Its reform is one aspect of wider UN reform being considered by a high level panel formed by the Secretary General Kofi Annan last year. It is due to report in December.

Why have Brazil, Germany, India and Japan formed a group?

They have formed a group called the G4 to argue for their collective claim and also for a permanent seat for an African country. In coming together in mutual support, they want to strengthen their chances and to raise their profiles above those of other countries which also have made a case.

They argue that their size and status - not least as large democratic countries - mean that they deserve permanent seats on the Council. They say: "The Security Council must reflect the realities of the international community in the 21st century." They also say that they have "the will and the capacity to take on major responsibilities with regard to the maintenance of international peace and security".

What are their individual cases?

Brazil: There is currently no seat for any Latin American country and Brazil argues that it is well suited to fill the gap. It has large trading interests and thinks that the needs of the developing world require greater attention.

Germany: Germany reckons that it has served its post WWII penance and that, given its economic power, deserves to be recognised as a world influence. It also has a specific argument that it pays a lot of the UN's bills.

Japan: Japan also says that it is a major payer of UN contributions. But beyond that it sees a role for itself as a major Asian power and as one which, like Germany, has deservedly emerged from its militaristic history.

India: India has for long had ambitions to be a regional power and reckons that it should play a role on the world stage as well. Its possession of nuclear weapons has not deterred the three other members of G4, all non-nuclear countries, from supporting its membership.

Who else has a case?

A consensus seems to be emerging that Africa has to have a seat. South Africa and Nigeria are obvious candidates. Tanzania is also putting itself forward. Egypt is also an African country but might be more easily considered for any Middle East representation.

In Asia, Indonesia is also a possibility. So is Australia. Argentina and Mexico argue that they too should be considered in Latin America.

The lack of any Islamic state on the Council is notable and will probably have to be addressed.

Will the G4 face opposition?

Since there are others who want a seat, the answer is probably yes. Within Europe, for example, Italy has expressed opposition for a seat for Germany. Some European federalists say that Britain and France should give up their seats and that there should be one seat for the EU. There is also unease among some right-wing conservatives in the United States about another seat for a European power.

The US supports Japan but China is wary about having a rival Asian power on the Council. Pakistan would not be too happy about a permanent seat for India.

On the other hand, Britain and France support the case made by the G4 for themselves and an African country.

Would new members of the Council have a veto?

Probably not and the old members would probably keep theirs as the price of reform. Reform of the UN involves bargains and it is unrealistic to think that the power of veto will change. But the Council could well be expanded in due course to about 25 with a better geographical and economic spread.

What about the reform of the UN more widely?

The "High Level Panel on Threats, Challenges and Change" reports on 1 December this year. It was formed by Kofi Annan when he said last year that the UN was at a "fork in the road."

It is likely to say that the UN must be more active in identifying and reacting to new threats, not just the ones identified by the West (terrorism and weapons of mass destruction for example) but ones of concern to poorer countries (like health and trade).

A key issue is whether the UN should be able to intervene in the affairs of member states more easily. It failed to do so, for example, to stop the massacres in Rwanda.

A concept named in a Canadian report as "The Responsibility to Protect" has gained some ground. It says that "sovereign states have a responsibility to protect their own citizens from avoidable catastrophe, but that when they are unwilling or unable to do so, that responsibility must be borne by the broader community of states".